Apparatus for internal forging of chain links



y 1959 J. w. SHEEHAN 2,893,199

' APPARATUS FOR INTERNAL FORGING OF. CHAIN LINKS Filed May 19. 1955 Y I2 Shet-Sheet 1 T C) Q IN V EN TOR;

BY v

ATTORNEX 2,893,199 APPARATUS FOR INTERNAL FORGINGVO-F CHAIN LINKS FiledMay 19. 1955 July 7, 1959 .1. w. SHEEHAN 2 Sheets -Sheet 2 INVENTOR. 1Jd772d M 5m BY v rr 7 5 W l 6 W W 5 a n #7 1 \1 u 5 Z I V O 2 W15 0 6 r7I AMA l 0 n 5 Q on W m Q United States Patent APPARATUS FOR INTERNALFORGING OF CHAIN LINKS James W. Sheehan, Pacific Palisades, Calif.

Application May 19, 1955, Serial No. 509,484

3 Claims. (CI. 59-30) eral object to provide an apparatus whereby suchsockets I may be forged in a conveyor chain link.

At the time the present invention was proposed, experts in the forgingart and in the conveyor chain art were of the opinion that to forgeinternal spherical sockets in the ends of a conveyor chain link would beimpossible. In spite of this opinion, the present invention has providedan apparatus whereby the internal forging of spherical sockets can notonly be successfully effected, but at a minimum of expense and whileholding dimensions within close tolerances.

Since the spherical bearing sockets cooperate with ball elements of theconnecting pins of a conveyor chain to provide for universal pivotalmovement, within limits, between the links of the conveyor chain,dimensional stability is an absolute requirement. Accordingly, one ofthe primary objects of my invention is to provide an apparatus by whichinternal spherical sockets can be forged accurately. A further object isto provide such an apparatus which will operate effectively within closetoleranc'es in reproducing large numbers of articles, i.e., which willmaintain close tolerances in production operation.

An important element of any industrial operation is of course theelement of cost. When the particular conveyor chain link which isproduced by the present invention was first envisioned, it was assumedthat a milling or machining operation would have to be utilized in orderto produce with satisfactory accuracy the bearing sockets in the ends ofthe link. Such a machining operation not only would be expensive, butwould cut the grain of the metal so as to leave surfaces havingunsatisfactory wear-resisting qualities, and therefore one of theimportant objects of the invention is to provide means for producingthese bearing sockets relatively inexpensively and at the same time insuch a manner as to produce hard, dense surfaces, highly resistant towear. The invention has achieved that object in providing a method andapparatuscapable of internally forging the bearing sockets in rapidsuccession. In general, this has been accomplished by providing anapparatus to effect a series of steps including (1) an initial forgingstep in which the general shape of the link, in rough form, is imparted;(2) a cleaning step to remove scale; (3) reheating the forged linkpreparatory to the internal forging operation; (4) hot forging theinternal sockets; and (5) simultaneously supporting the external endsurfaces of the link against deformation resulting from the forgingpressure applied to the inner end surfaces, and reshaping said externalsurfaces to their final shape.

, This invention is directed particularly to the fabricating .of thecentral links of the conveyor chain disclosed in my US. Patent No.2,600,174, issued June 10, 1952. The present invention provides animportant improvement in the chain, in the utilization of spherical endsurfaces on the center link, said end surfaces bearing against the teethof a drive sprocket with a bearing engagement that transmits the drivingforces of the sprocket teeth directly to the centers of the connectingpins of the chain, without developing any appreciable lateral movementsof force tending to tilt the link in one direction or the other from itsline of driving forces. Such lateral 'rnoments of force cause the linksof conventional chains to assume canted positions along the line ofdrive and often result in breakage of links. In my improved chain theend bearing surfaces of the links are spherical and coaxial with theinternal spherical bearing surfaces thereof, and as a result, the abovedescribed difliculties are avoided.

It is not practicable to shape the end surfaces of the link to thisspherical shape in the initial forging step, since to attempt to do sowould cause the forgings to adhere to the die members. This inventionprovides a fabricating apparatus wherein, in the initial forging step,the end surfaces of the links are shaped with conventional draft angles(e.g. seven degree conical departure from cylindrical shape) on eitherside of a parting plane. The utilization of the draft angle facilitatesthe forging of the links with maximum ease and provides for readyremoval of the links from the forging dies. These seven degree draftangles are observed not only externally but also internally, includingthe inner end areas of the links which later are formed with thespherical sockets. That is to say, in the initial step, these inner endsurfaces are convex in contrast to their final concave form. In thefinal step, these convex inner end surfaces are changed to the concavespherical bearing surfaces. This requires moving an appreciable amountof metal, and one of the important objects of the invention is to dothis with a minimum of strain upon the dies, with a minimum powerrequirement, and with maximum speed and accuracy. The invention achievesthese results by utilizing clearance spaces (between the initialfrusto-conical draft angle end surfaces of the link and the sphericalfemale die recesses which give the end surfaces their final shape) toreceive the metal that is pushed outwardly in the forming of the bearingsockets. Accordingly, the bearing sockets are formed simultaneously withthe reshaping of the outer end surfaces of the links, so that thenecessity for coining or extruding metal laterally is reduced, and theshaping of the bearing sockets is a hot forging step in which i themetal is pushed radially outwardly to fill the die recesses which shapethe outer end surfaces of the links. As contrasted to the common coiningor extruding operation in which the metal must be subjected to extremelyhigh pressures to cause it to actually flow, the final step of operationis one in which the forging action involves a substantial element ofshaping or forming (bending) action.

One of the important objects of the invention is to provide a forgingapparatus by the use of which it becomes possible to hold chain pitch tomuch closer tolerances than have hitherto been possible. This isaccomplished through control of the spacing of the spherical end bearingsurfaces of the link, in the final re-shaping operation against theseend bearing surfaces. By holding closer pitch tolerances, I provide achain which is smoother in operation andmuch less subject to fluctuatingstrains thereon in operationtherefore less vulnerable to wear.

Another object of the invention is to provide an improved conveyor chainof the universally pivotal type having links, the outer end faces ofwhich are spherical so as to receive the driving pressure of sprocketteeth without developing any substantial lateral component of force suchas would tend to cant the link away from its line of drive.

Other objects will become apparent in the ensuing specificationsand"aended drawings" inwhich:

Fig. 1 is a plan view of the apparatus of my invention;

Fig. 2 is a front view of the same;

Fig. 3 is a sectional view'take'non the line 3-3 of "Pi [2;

Fig; 4 is a detail sectional view of'acentral portion of the "apparatustaken 'on' the line'4'4 of Fig; 3;

The particular chain link for which the present apparatus is especiallyadapted, is the center'link (indicated generally at 7) of the chainwhich forms the subject matter of my above identified patent; Le, auniversally pivotal'chain comprising aseries of such center links, apairof side linksfor each center link, and-pivot pins for joining thelinks in end to end' succession, with the center linksdisposed'-between"pairs of side links and the-pivotpins having centralball elements that bear in spherical bearing sockets 8 in the respectiveends of the links 7. Fig. 9 illustrates the final spherical shape (indicated at 59) of the outer end bearing surface of the link 7, againstwhichsprocket teeth may bear so as to transmit driving force radi'ally'to the'center of pivotal movement of the link on a' connecting pin,avoiding any lateral components of forcethatin an ordinary chain tendto' cant the links out of the line ofdrive and thereby greatly increasethe strain thereon.

I The apparatus 'As an example of onevform of the apparatus that maybe"utili'zed in carrying out the invention, I have shown in'Figs. 1-6 ofthe drawing a reshaping apparatus applied to a punch press having a base9, a bed 10 supported thereon, and a ram 12 which is reciprocatedvertically by power mechanism (not shown). My improved apparatusincludes two assemblies, namely .a lower die assembly the parts of whichare mounted on a shoe 13, and arec'iprocating actuatorcam unit, which ismounted on'the ram' 12 and is indicated generally by the referencenumeral 14. The shoe13 is fastened upon the bed 10 in aconventional'manner by anchor bolts 15.

The die assembly includes a pair of opposed female die blocks 16slidably mounted on a pair of parallel rails 17 and each having a dierecess 18 to shape an end of the chain link.

Lateral support is given to the thinner portions 19 of the side armsoflinks 7 by means of a pair of side bucking'blocks'20, secured, as bymeans of screws 21, to each die block 16 in laterally spacedarrangement, the space between the blocks 20 registering with the mouthof recess 18.

The thin arm portions 19 of the link define elongated openings 22extending from the bearing sockets 8 to shoulders 23 (extremities of thecentral thicker portions 24 of the side arms). 'The inner walls ofthinned portions 19 are convex, parallel, and tangent to the majorcircumference of sockets 8. This makes it possible to introduceintoopenings 22a pair offorgingheads 25, each having a spherical peen 26for shaping a socket 8, 'and conical or bevelled faces 27 for shapingbeveled faces 28 at'the edges of the bearing socket 8. The major widthof aforging head 25 is just slightly less thanthe width of an opening 22as it exists in the rough-forged blank, so that the heads mayfreely'slide into'open'ings' 22 as the' link 7 is droppe'ddo'wnwardly"into the'die "from above.

Forging heads 25 are formed on the upper ends of posts 30 each'of whichconstitutes a relatively narrow portion of a male forging unit ofinverted T-shape, and projects upwardly from the center of a crosshead31 that constitutes a relatively broad base portion of such unit, and isslidably mounted on rails 32. Rails 17 and 32 are mounted at their endsin brackets 33 which at their lower ends are attached to the mountingshoe 13. Intermediate their .ends,..the brackets 33 are connected by-abridge plate 34 which is seated upon shoulders 35 in therespective-brackets. Thebridge plate 34 not only acts as a brace'betweenthe brackets 33, but also serves as a guide for the forging heads25,which are embraced between the walls of a.slot.36 extendinglongitudinally therein.

In the normal, inoperative positions of forging heads 25, shown in Figs.1, 4 and 5, the heads are withdrawn toward each other from the bearingsockets 8. .In the forging operation, they move away from each otherinto engagement with the inner end walls of the link 7, against theyielding resistance of coil springs 37 which encircle the guide rails 32and act under compression between the brackets '33 and the crossheads'31, tending to move the forging heads toward each other to theirinoperative positions.

The forging heads 25 are moved to their operative positions by a wedgeshaped actuator cam 38, the sides of which engage inclined cam faces onthe backs of the respective forging heads 25. The actuator cam 38 ismounted on the bottom of a crosshead 40 which in turn is mounted onram12. Projecting downwardly from the ends of crosshead 40 are a pair ofbucking jaws 41 which are received in central recesses 39 in brackets33, and engage the backs of female die blocks 16 as indicated in dottedlines in Fig. 4 and. force them against the outer end faces of the link7' to shape said end faces to their finished contours and dimensions.

Movement of the die blocks 16 back and forth between their operativepositions engaging the ends of links 7 and their inoperative'positionswithdrawn from the ends of the links, is effected by the cooperativeaction of bucking blocks 41 and two pairs of coil springs 42, exerting apull against respective yokes 45, to which pairs of links 46 arepivotally connected by pivots 47 and are pivotally connected to theendsof a respective die block 16 by pivots 48 Coil springs 42 have theirouter ends anchored to brackets 49 which are mounted on shoe 13. Thecoil springs are extended under tension.

Operation of the apparatus In the process of fabricating a conveyorchain link in accordance with my invention, the link 7 is first forgedin an initial forging step in which it is given the rough shape shown inFigs. 7 and 8. Instead of the sockets 8, there is a semi-circular ridge53 terminating at the outer extremities of the openings 22. Theentireouter periphery of the link, the openings 22, shoulders 23 andinner faces of the thickened central arm portions 24 are shaped with aconventional draft angle (ordinarily about seven degrees). That is, theinner and outer faces of the link are each defined by two surfaces whichcooperatively define a dihedral angle the apex of which constitutes aparting line. The parting lines are indicated at'54 in Fig. 8, whichshows the rough forged link prior to the finishing step. It will benoted that the cross section. of the end of the link indicates pairs offrustoconical surfaces intersecting at the parting line, whereas in thefinished link shown in Figs. 4, 5 and 9, the end surfaces 59 arespherical (convex and concave respectively). The initial forgingoperation is of a conventional nature, utilizing opposed forging dieswhich meet ata parting plane which constitutes the general plane of the.link (at right angles to the axes of openings22). Since these forgingdies move in a' direction parallel to .the axes .Of open ngs}; it isobviouslyimpossible for them to form thebearmg sockets 8. The surfacesof ridges 53 are therefore of convex cross sectional shape, as shown inFig. 8, instead of the concave shape of sockets 8.

In the next step, the link 7v is allowed to cool and it is then immersedin a cleaning bath to remove scale.

In a succeeding step, the cleaned link is reheated to a cherry red butwithout reaching a temperature sufficient to cause it to lose its shape.As soon as the link is heated to the proper temperature, the workmangrasps it with a suitable pair of tongs and transfers it to thefinish-forging apparatus shown herein. Care is taken to see that the dieblocks 16 are withdrawn to their inoperative positions, and the ram 12is of course in the elevated position. The link 7 is fitted into thespaces defined between the retracted forging heads 25, die block sockets18 and lateral support blocks 20. The shoulders 55 engage the underedges of side arms 24 of the link 7, and support the link at a fixedheight when the die heads subsequently advance into engagement with theends of the link.

vAfter the workman is sure that this link is properly bottomed, heoperates the punch press to cause ram 12 to' descend, bucking jaws 41effecting a camming action against the die blocks 16, moving them intoengagement with the ends of the link. This is the next step of theprocess, the advancing movement of die blocks 16 being accurately gagedby the camming action so that the advancing movement of die blocks 16 isarrested at exactly the proper position to causethe walls of dierecesses 18 to snugly engage' the ends'of the links 7, applyingdeformingpressure thereto. 7, t

In the same step of the process, theforging heads 25 are moved apart bycam 38 into engagement with-the ridges of metal 53 in the ends of thelink 7, to forge the replicas of faces 27 and 26 in the ridge 53 whichprovides justsufiicient metal for extrusion into the furrows betweenfaces 26 and 27, leaving the bearing sockets 8 and relief faces 28accurately formed and intersecting each other in sharply defined ridges57.

Theme-shaping operation is effected by a single blow of each forginghead 25, produced by forcing the actuating cams 38 downwardly betweenthe cam faces 39' of the forging heads, in a descending movement of ram12. As the forging heads are moved apart, the bucking jaws 41 will forcethe die blocks against the outer end faces of the link, shaping them totheir spherical contour. The operation is carried out without in any waydistorting the link from its true shape.

The press ram 12 is allowed to complete one full cycle of movement(descending movement followed by an upward withdrawal) which allows theforging heads 25 to be retracted by springs 37 to the positions shown inFig. 4, in which they allow the extremities of sockets 8 to clear themas the link 7 is lifted out of the die assembly. At the same time,bucking jaws 41 are retracted upwardly, allowing springs 42 to withdrawthe die blocks 16 to the inoperative positions. These positions aresomewhat farther apart than those shown in Figs. 4 and 5, which show thedie blocks in intermediate stages of movement toward each other, asindicated by arrows 58. The completely retracted positions are shown inFigs. 1 and 2. The link is then lifted from the re-shaping apparatus.This becomes possible because the forging heads 25, in their retractedpositions, will clear the extremities of ridges 57 which define thesides of the sockets 8. The workman then inserts a fresh link in there-shaping apparatus and the above described cycle of operation isrepeated.

It will be apparent from the foregoing that each reshaping operationinvolves simply a single stroke of a punch press. Aside from the timeconsumed by the cycling of the press, the speed with which the socketsmay be forged in the links is therefore limited only by the speed atwhich the operator can insert the links into the re-shaping apparatusand remove them. Access to the inner end walls of the links is gained byfirst effecting relative movement between the links and the forgingheads in a direction parallel to the axes of openings 22 while theforging heads are centered in the openings'22; then effecting movementof the forging heads 25 longitudinally of the links, from the openings22 into the end spaces within the links; then forging the sockets; thenwithdrawing the heads in the opposite directions back into registry withthe openings 22; and finally withdrawing the link by effecting relativemovement between the forging heads and link in a direction parallel tothe axes of openings 22. Adequate forging pressure is derived frompowerful blows of a punch press ram, multiplied by the camming action ofcams 38 against cam faces 59. Thus the cams 38 function not only toeffect the spreading movement of forging heads 25 which is essential tobring them into engagement with the ends of the links, but also tomultiply the pressure of the blow delivered by the ram in order toobtain adequate pressure. Distortion of the link under these heavypressures is avoided by completely supporting the ends of the link inthe embrace of die recesses 18 and lateral bucking blocks 20, backed upby the bucking jaws 41.

It is to be understood that by making the guide rods 32 and the hearingsin the orossheads 31 sufficiently sturdy and large inarea, it may bepossible to eliminate the upper guide rods 17. Thus the elements 17 maybe regarded as improvements in the basic structure but not completelyessential elements.

,I claim:

1. Apparatus for forging a pair of spherical sockets in the internal endsurfaces of a conveyor chain link having end loops and thickened centralarm portions the ends of which are in the form of shoulders cooperatingwith said end loops to define a pair of elongated openings the endextremities of which are defined by said internal end surfaces, saidcentral arm portions defining between them a central space of less widththan said openings, said apparatus comprising: a pair of end brackets; apair of rails secured to and extending longitudinally between said endbrackets in laterally spaced parallel relation in a common horizontalplane; a bridge plate secured to and extending longitudinally betweensaid end brackets above said rails and parallel to said plane, saidbridge plate having a slot extending along the longitudinal axis of theapparatus; a pair of guide rods secured to and extending longitudinallybetween said end brackets above said bridge plate; a pair of maleforging units each comprising a relatively broad cross head having apair of laterally spaced bearing bores through which said rails extendfor guiding said cross head for longitudinally approaching and recedingmovements; forging finger formed integrally with and extending upwardlyfrom each respective cross head through said bridge plate slot andlaterally supported and guided therein and having a forging head at itsupper end; a pair of female die blocks each having a pair of laterallyspaced bearing bores through which said guide rods extend for guidingsaid die blocks in approaching and receding movements; said forgingheads each having a forging face corresponding to the shape of thesocket to be forged and a thickness greater than the width of saidcentral space of the link; said die blocks each having a U-shaped recessfor shaping a respective external end surface of the link and eachhaving, at the bottom of its recess a pair of laterally spacedsupporting shoulders for supporting respective side portions of the linkwith said internal and external end surfaces thereof in registrationwith said forging heads and female die recesses respectively; yieldingmeans acting between said end brackets and the respective cross headsfor yieldingly urging the latter toward one another and normallymaintaining said forging heads in position to pass through said endopenings of the link as the latter is inserted into the apparatus; meansacting yieldingly against said female die blocks for normally spreadingthem to positions for freely receiving the end loops of the link; andmeans for simultaneously spreading said forging heads and drawing saidfemale die block inwardly for forgingengagement with said internal andexternal end surfaces of r the link respectively.

'2..Apparatus as defined in claim 1 wherein'said first mentionedyieldingmeans comprises coil springs encirclingsaid rails'and engaged undercompression between said end brackets and said cross heads; and whereinsaid second mentioned yielding means comprises tension springspanchor'members to which the outer ends of tension-springs'areattached;and linksconnecting the inner ends ofsaid tensionsprings to the respective dieblocks. -3. Apparatus for iorging a pair of spherical sockets in'theinternal -endsunfaces of a conveyor chain link having-end loopsandthickened central arm portions the ends or whichare in theform ofshoulders cooperating with said endloops to definea pair of elongatedopenings the end'extremities of which are defined'by' said internal endsurfaces, said central arm portions defining between them 'a'centralspace of less width than said openings, said apparatus comprising:support means having longitudinally spaced supporting parts; a bridgeplatesecured to-andextending between said supporting parts in a hori-Zontal plane and having a pair of opposed bearing walls definingaguideslot extending along the longitudinal axis of the apparatus; a pairof male forging units of inverted T shape each' including a relativelybroad horizontally extending cross head as a base portion thereof and arelatively narrow finger projecting upwardly therefrom through saidslotand laterally supported by said bearing walls-and guided :in saidjslot,saidrcross head including portions extending laterally beneath saidbridge plate onrespective sides of said slot, said finger having alforginghead corresponding to the shape of the socket to*be"forged-and-having a thickness greater "than the widthpf said central space;means beneath said bridge plateslid'ably mountingandguiding said crossheads'with saidfor'ging units inopposed relationship for receding andadvancingmovement with reference to each other along a'longitudinalaxis; said forging heads when re- 8 tractedbeing'positionedto entersaidopenings}intl1e;link whilespaced from said internal -en'd=-surfaces;apair of female die blocks each having a uvshaped --recessfor shaping arespective external. end surface of the-link and each-having,- at-thebottom of I said recess, onrespective sides thereof, a pair of laterallyopposed shoulders for supporting 'saidend loops at respective sidesthereof adjoining said thickened central arm portions of the link; aspreading wedge insertable into said central spaceof the link-forengagement with said forgingheads to spread them into engagement withsaid internal end surfaces of the link to forge said socketsya pair ofbucking jaws in spaced relation to 1 respective sides of said spreadingwedge along a common longitudinal axis, for engagement with the. backsof saidfemale die-blocks to move them inwardly into engagementwith'theexternal *surfaces of said end loopsforreshapingsaid external endsurfaces while supporting said cnd loops against the forging pressure ofsaid-forging headsy-and-a' common support to whichsaid wedge and jawsare rigidly attached, said common support 'functioning' for moving saidwedge and jaws into engagement with said forging headsand femaledie'blo'cks, under the"-force;of a blow delivered by a punch press.

References-Cited in'the file of this patent UNITED STATES PATENTS

